Waste

Johannesburg Water has to ensure that all wastewater discharged into its sewers and conveyed to its treatment plants is treated to the highest standards before being discharged into the natural environment.

The purifying standards are enforced by the national Department of Water Affairs and Forestry (DWAF), and are among the highest in the world.

As part of the process to ensure that the wastewater is conveyed to treatment plants without leaking into the environment, Johannesburg Water cleans 144km of sewers and clears more than 3 000 sewer-blockages every month.

There are six wastewater treatment plants across the city, the largest being the Northern Works. It treats 400 million litres of wastewater every day from around 1,6 million people. This plant serves the area north of the Hillbrow ridge including Alexandra, Edenvale, Randburg, Sandton and parts of Midrand and Roodepoort. It is situated in the Diepsloot area.

The treated effluent from this plant is either discharged into the Jukskei River, used to irrigate Johannesburg Water’s farm lands, or pumped to the Kelvin Power Station for use as cooling water. This ensures that expensive high quality drinking water is not used for this purpose.

System Cycle

The Northern Works makes use of a sophisticated locally developed technology which uses natural biochemical processes. City scientists and engineers have, over many years, developed and refined a biological wastewater treatment process that removes organic pollutants as well as nitrogen and phosphorus.

The system is recognised internationally as the "Johannesburg Process".

The quality is continuously controlled and monitored.

In addition, Johannesburg Water has found a use for the 100 000 dry tons of wastewater sludge produced yearly at the treatment works. Johannesburg Water produces a compost by-product – JO-GRO – made from the sludge and waste wood from the tree-felling industry. The technology to convert sludge into compost was adapted from technology used by many US cities.

JO-GRO is free of disease-carrying organisms and a good product in horticulture and agriculture. As well as containing the usual plant nutrients it contains trace nutrients and agents that suppress plant diseases and pests.

Natural Cycle

This means that potable water for the region, which is purchased in bulk from Rand Water, has to be pumped up about 50 km from the region of the Vaal River.

The advantage of being on a ridge is that much of Johannesburg's wastewater can flow by gravity to its treatment works.

Wastewater treated in Johannesburg Water’s treatment plants is discharged into one of two catchments: the Jukskei/Crocodile River catchment in the north; and the Klip/Vaal River catchment in the south. Both catchments are classed as sensitive to the discharge of waterborne pollutants.